Vapor phase hydrolysis of materials to form hydrogen represents a commercially viable strategy for a fuel cell system capable of achieving volumetric and gravimetric energy density several times greater than that of lithium polymer batteries. One limitation of this technology is the very slow reaction rate of the fuel with water vapor. To achieve high volumetric energy density, the fuel must be pressed into pellet form; however, once in pellet form the fuel is even slower to react and produce hydrogen. Slow hydrogen production can result in very low rate capability of the fuel cell rendering the technology inadequate for applications relying on higher power to be commercially viable. Although the surface area of the hydrogen-generating material can be increased, or the amount of hydrogen-generating material can be increased, this can result in higher cost, lower energy density, and can increase the size of the product to a point where it is too large to be commercially feasible for traditional consumer electronics such as smart phones.
Another limitation of vapor phase hydrolysis to form hydrogen for a fuel cell system is the formation of unwanted products from the material being hydrolyzed such as hydrated hydroxides. Hydrated hydroxides form when temperature and humidity conditions are in a range where hydrated hydroxides form during the reaction instead of the desired unhydrated hydroxide. When byproducts such as hydrated hydroxides are formed, the hydrogen-generating material can take on additional mass which reduces gravimetric energy density. The formation of byproducts such as hydrates also results in significant volume expansion which reduces volumetric energy density. In addition, byproduct formation such as hydrate formation can result in reduced hydrogen generation rate capability as water that could be used for hydrogen generation can be bound as a hydrate or other byproduct.